Fisk was medical director, Life Extension Institute; Crawford was Assistant Medical Director, Life Extension Institute. "This pioneering monograph on the value of periodic health examination includes numbers of photographic illustrations depicting the examination of patients. The concept of comprehensive routine health examinations was first promoted aggressively in the twentieth century. It was one factor that contributed to the growth of cardiology as a specialty" (W. Bruce Fye). See Fye, American cardiology, 37-44.